Show exactly what this looks like, with a practical example. Something as seemingly simple as "deleting edges" can mean very different things depending on how it's done.
* But wait, I lied! technically some triangles are more expensive than others to render. A long thin tri that overlaps lots of other tris would be more expensive, for example. Manually triangulating the mesh to avoid these triangles would be the best way to fix this. But with multi-million-polygon engineering CAD…